Background-The cause of dementia in subcortical ischemic vascular disease (SIVD) is controversial.

Triple-negative breast cancers with elevated MYC are sensitized to CDK inhibition.

The telomerase ribonucleoprotein complex caps chromosome ends by adding telomeric repeats. Here we show that catalytically active human telomerase has a regulated intranuclear localization that is dependent on the cell-cycle stage, transformation and DNA damage. In primary cell lines, low expression of a fusion protein of green fluorescent protein and telomerase reverse transcriptase (GFP-hTERT) increases telomerase activity and stabilizes the maintenance of telomere length. Confocal microscopy shows that the release of telomerase to the nucleoplasm from sequestration at nucleolar sites is enhanced at the expected time of telomere replication. By contrast, in tumour and transformed cells, there is an almost complete dissociation of telomerase from nucleoli at all stages of the cell cycle. Transfection of the simian virus 40 genome into a primary cell line is sufficient to mobilize telomerase from nucleoli to the nucleoplasm. Conversely, ionizing radiation induces the reassociation of telomerase with nucleoli in both primary and transformed cells. These findings show that transformation and DNA damage have opposite effects on the cellular regulation of active telomerase, affecting the enzyme's access to both telomeric and nontelomeric substrates.

A family of conserved serine/threonine kinases known as cyclindependent kinases (CDKs) drives orderly cell cycle progression in mammalian cells. Prior studies have suggested that CDK2 regulates S-phase entry and progression, and frequently shows increased activity in a wide spectrum of human tumors. Genetic KO/ knockdown approaches, however, have suggested that lack of CDK2 protein does not prevent cellular proliferation, both during somatic development in mice as well as in human cancer cell lines. Here, we use an alternative, chemical-genetic approach to achieve specific inhibition of CDK2 kinase activity in cells. We directly compare small-molecule inhibition of CDK2 kinase activity with siRNA knockdown and show that small-molecule inhibition results in marked defects in proliferation of nontransformed cells, whereas siRNA knockdown does not, highlighting the differences between these two approaches. In addition, CDK2 inhibition drastically diminishes anchorage-independent growth of human cancer cells and cells transformed with various oncogenes. Our results establish that CDK2 activity is necessary for normal mammalian cell cycle progression and suggest that it might be a useful therapeutic target for treating cancer.analog-sensitive kinase | cyclin-dependent kinase